I will never run a spring tensioner on a chinagirl kit. Its not that hard to get the sprocket centered which removes the need for this band-aid fix. Some bikes require a tensioner, but a spring loaded one is asking for trouble somewhere down the road.
All a spring does is make it LOOK tight, everytime you let off the throttle, there's all the slack on the top chain run.
Take the time to center whatever sprocket you use and you don't need a spring.

I think your wrong on several points.

Getting the sprockets lined up with the rag adapter is a real
problem and furthermore driving the bike by the spokes is flinstone technology. Using the hub adapter allows for lateral adjustment to get perfect alignment between the the sprockets. Even if your able to get perfect alignment initially with the rag, its just a matter of before everything goes haywire.